The present invention relates to the structure of a heat insulating hose adapted to be used mainly as an air-conditioner drain hose.
A heat insulating hose having a structure in which a belt material of a foamed synthetic resin cut to have a predetermined width is spirally wound on the outer circumferential surface of an inner tube while the cut surfaces of the belt material are made to abut one another and then a synthetic resin tape is spirally wound on the outer surface of the belt material so as to cover the belt material is generally well known and used as a conventional heat insulating hose. Further, a technique of a heat insulating pipe in which a foamed plastic belt material is put longitudinally on the outer circumferential surface of a straight pipe and rolled into a cylinder and the opposite side edges of the rolled belt material are joined in the axial direction to thereby form a heat insulating coating layer is also proposed as a known technique. Further, an inner tube in the form of a bellows tube which has an annular-shaped portion protruded outwardly in a circumferential direction in order to have flexibility is known.
The well-known heat insulating hose of the former type was not always excellent in productivity because the hose had to be formed while a foamed synthetic resin belt material and a coating tape were wound spirally or while parts of the coating tape were laid to overlap each other and adhesively bonded to each other particularly in the case of the coating tape. On the other hand, the heat insulating pipe of the latter type has a merit that the productivity can be improved because the heat insulating pipe is formed in a manner that a heat insulating material is put along a core pipe longitudinally and the opposite ends of the heat insulating material are joined to each other longitudinally. The latter heat insulating pipe, however, has a problem that the heat insulating pipe is poor in heat insulation because the heat insulating material applied on the inner tube is moved relative to the inner tube so as to be separated from the inner tube easily so that a space is produced between the heat insulating material and the surface of the pipe.